courtesy (waiter laugh or bartender laugh) laugh 

when a waiter or bartender is working in a very loud bar or restaurant and cannot completely hear what the customer is saying but they start to laugh when they thought it was a time to insert laughter.
also known as a courtesy laugh when a customer says something at all remotely funny so you use the waiter laugh or bartender laugh to make the customer think they are funny.

I was table-side when the family was talking to me and I started using my "courtesy (waiter laugh or bartender laugh) laugh" when Mr. Young told the same story he has told 45 times previously.

courtesy (waiter laugh or bartender laugh) laugh by dakine mahalo December 2, 2009